The invention relates in general to automotive multimedia systems, and in particular to an automotive multimedia system having a local network with several subscribers connected together into a ring network by an optical data line, to transmit and receive compressed data of various types.
Local networks with several subscribers connected together into a ring network by an optical data line, to transmit audio, video and/or control data are known, for example, from European Patent EP 519 111 B1. The local network disclosed therein has several subscribers, some of which generate audio or video data and control data, and provide the data into the ring network. The subscribers that generate such data are typically referred to as data sources. Other subscribers to the network receive the data intended for them from the network, and then present the data to a user, for example, by acoustic or visual reproduction. The subscribers that receive such data are often referred to as data sinks.
The known local networks have various data sources such as, for example, a car radio, CD player, DVD player, or a TV tuner, which typically transmit their data uncompressed over the optical data line to the appropriate data sink, for example a car amplifier to which several loudspeakers are connected, or a screen which displays the uncompressed FBAS video signal. The subscribers to such a network input their data to the network independently of one another and thus sometimes simultaneously, and withdraw the data in the same manner. Consequently, such a network can accommodate only a few subscribers at any one time since the transmission capacity of the network over the data line is inherently limited.
Individual devices are known, for example a television having a TV tuner and picture tube in a housing, and which are connected to one another via a data line. Uncompressed video signals are transmitted through the data line (e.g., as FBAS signals), and are displayed on the picture tube. Device combinations are also known, for example a DVD player with a television set. With this combination, the compressed data stored on the digital video disk (DVD), which are coded, for example according to the MPEG-2 standard, are read and decoded and decompressed by an appropriate MPEG-2 decoder in the DVD player. The decompressed data are then transmitted over the connecting data lines to the television set which reproduces and displays these decompressed data, for example as an FBAS signal, in accordance with the video data received by the TV tuner. A problem with the prior art systems is that the data on the data network are not compressed and thus make inefficient use of the bandwidth of the data line, and further require the data sources to provide decompressed data to the data sinks.
What is needed is a data network that connects several devices together and transmits and receives compressed data over the network.